Our long-term goal is to define the fundamental mechanism of the systemic autoimmune disease (SLE) and malignant B cell lymphomas that develop spontaneously in the crosses between NZB and the normal SWR mouse strains. The etiologic mechanism of Systemic lupus erythematosus (SLE) remains elusive because the primary antigen that triggers the pathogenic autoimmune response in this disease is unknown. In spite of this obstacle, we have cloned the select T and B cells that are pathogenic in SLE. Analyses of the structure and specificities of the receptors expressed by these particular T and B cells that are representative of the disease and studies of their regulation may lead to an understanding of the etiologic mechanism of lupus. The major goals of this application involve: 1) Pathogenic B Cells: (a) Define the structural basis of cationic charge, antigenic specificities, idiotypic cross reactions and clonal relationships among pathogenic anti-DNA autoantibodies. b) Study the germline V gene repertoire that generates the pathogenic autoantibodies, define the natural specificities of antibodies encoded by these germ line V genes and determine the degree of somatic mutations required to generate the pathogenic autoantibodies. c) Determine if the lupus-prone mice have an intrinsic B cell defect in tolerance induction or in Ig somatic mutation mechanisms using transgenic mice carrying autoantibody V genes. 2) Pathogenic T Cells: (a) Determine the V region sequences of the receptors (TCRs) expressed by the pathogenic autoantibody-inducing T cells to detect any clonal restriction/recurrent usage or any special feature in their junctional region (CDR3) sequences that would provide clues for their antigenic specificities. b) Determine the specificities of these T helper cells that preferentially interact with the pathogenic autoantibody-producing B cells, using synthetic peptides and B-B hybridomas. c) Attempt to block the pathogenic autoimmune response in vivo by rendering the autoimmune T helper cells anergic. These studies will help us to design specific therapies that could intervene in the basic steps leading to systematic autoimmune disease in lupus and may direct similar approaches for other rheumatic diseases where the inciting antigen is unknown. Furthermore, understanding the nature of the intrinsic B cell abnormally in these NZB crosses could help elucidate the mechanism of B cell lymphoma development in these mice.